In a photolithography process for a semiconductor wafer (hereinafter referred to as a “wafer”), a resist film is formed on the surface of the wafer and is exposed with predetermined patterns. Thereafter, the resist film is developed to form a resist pattern on the resist film. In order to remove a resist residue generated during the developing process, a cleaning liquid is supplied to the wafer to clean the wafer. After supplying the cleaning liquid, the cleaning liquid on the surface of the wafer is removed by rotating the wafer. As a result, the wafer is dried.
For example, pure water is used as a cleaning liquid. Since the pure water has a relatively large surface tension, the resist pattern collapses, namely from the destruction of wall portions constituting the patterns. This may occur due to the capillary phenomenon generated in removing a cleaning liquid between the resist patterns. In order to suppress the pattern collapse, a liquid relatively low in surface tension (referred to as a “low-surface-tension liquid”) containing a surfactant is supplied to a wafer after the pure water is supplied. The removing process is performed while replacing the pure water between the patterns with the low-surface-tension liquid.
However, it is known that the surfactant contained in the low-surface-tension liquid percolates into the space between the resist patterns causing the resist to swell, thereby resulting in a change in the CD (Critical Dimension) which is the line width of the resist patterns. It has been determined that fine resist patterns may be formed by EUVL (extreme ultraviolet lithography), i.e., a lithography in which exposure is performed using extreme ultraviolet radiation (EUV). Under these circumstances, a technology capable of suppressing the pattern collapse and then additionally minimizing the change in the CD is needed. Meanwhile, a hole may be formed in a layer of a cleaning liquid on the substrate surface by supplying a gas to the central region of a rotating substrate, and the substrate may be dried by enlarging the hole. However, this method cannot also solve the aforementioned problem.